Functional ultrasound (fUS) is brain imaging technology which uses ultrasound imaging to detect movement of blood in the brain, which can be used to make a functional image. It has the combined advantages of EEG and fMRI processes, allowing for both high temporal and spatial resolution (Macé et al., 2011).
In general, ultrasound imaging techniques work by transmitting ultrasound waves to tissues in the body and detecting the changes in the echoes of the waves which bounce back. In fUS, this technique is optimized for detecting changes in cerebral blood flow. If a brain area is more active, it will require more glucose and oxygen, which must be carried to it by blood. Therefore, increased activity in a brain region will require increased blood flow to that region. Using fUS, blood flow to distinct regions can be measured and used to infer which brain areas were more or less active during a period of time (Macé et al., 2013).
This follows a similar idea to fMRI, which measures the amount of oxygenated and deoxygenated blood in distinct brain areas. However, fUS has many advantages over fMRI, since it is less expensive, does not require intense magnetic fields, and has much better temporal resolution (Zheng et al., 2023). Furthermore, fMRI machines are huge and noisy, and contain extremely strong magnets. Making this into a wearable technology would be very difficult, especially because of the strong magnets involved.
Throughout our examination of wearable neuroimaging technology in this course, we have mainly discussed and used Muse headsets, which utilize EEG and fNIRS. This technology is very portable and can be useful for many applications, but I feel that it is limited by the fact that it has very low spatial resolution. Techniques like EEG measure whole-brain activity in real-time, which make it very useful for neurofeedback applications. However, it is impossible to isolate and compare activity in different brain regions using this approach.
I believe that fUS presents an opportunity to combine the benefits of EEG and fMRI technology into a portable, wearable system. This would be transformative because it would allow for region-specific insights into brain activity in daily life, allowing for much more precise and useful brain data to be recorded by users. It would also allow for researchers to gain region-specific brain data without the requirement of large in-lab machinery, opening the door to many different kinds of studies which were previously not possible. Naturalistic studies in humans using fUS imaging have already been done, but required the device to be physically implanted beneath the skull (Soloukey et al., 2025). Creating a non-invasive wearable device would allow these same methods to be replicated in a broader sample of people.